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The two-dimensional measurement of the angular correlation of the positron annihilation radiation (2D-ACAR) is a powerful tool to investigate the electronic structure of materials. Here we report on the first results obtained with the new…

Strongly Correlated Electrons · Physics 2015-06-15 Josef Andreas Weber , Peter Boni , Hubert Ceeh , Michael Leitner , Christoph Hugenschmidt

The electron-positron annihilation spectrum observed by SPI/INTEGRAL during deep Galactic Center region exposure is reported. The line energy (510.954$\pm$0.075 keV) is consistent with the unshifted annihilation line. The width of the…

Astrophysics · Physics 2009-11-10 E. Churazov , R. Sunyaev , S. Sazonov , M. Revnivtsev , D. Varshalovich

Angular Correlation of Annihilation Radiation (ACAR) is a well established technique for the investigation of the electric structure. A major limitation of ACAR studies is the available positron flux at a small spot on the sample. Fore this…

Instrumentation and Detectors · Physics 2012-10-15 Hubert Ceeh , Josef-Andreas Weber , Michael Leitner , Peter Böni , Christoph Hugenschmidt

Precise measurements of spectra of cosmic ray electrons and positrons can effectively probe the nature of dark matter (DM) particles. In a class of models where DM particles initially annihilate into a pair of intermediate particles which…

High Energy Physics - Phenomenology · Physics 2018-09-26 Lei Zu , Cun Zhang , Lei Feng , Qiang Yuan , Yi-Zhong Fan

Cosmic-ray positrons have long been considered a powerful probe of dark matter annihilation. In particular, myriad studies of the unexpected rise in the positron fraction have debated its dark matter or pulsar origins. In this paper, we…

High Energy Astrophysical Phenomena · Physics 2022-01-07 Isabelle John , Tim Linden

The precise measurements of energy spectra of cosmic ray positrons and/or electrons by recent experiments show clear excesses above 10 GeV. Moreover, a potential sharp spectral feature was suggested by the Dark Matter Particle Explorer…

High Energy Physics - Phenomenology · Physics 2020-04-29 Lei Feng , Zhaofeng Kang , Qiang Yuan , Peng-Fei Yin , Yi-Zhong Fan

We propose a method to ease the challenges of exploring multi-dimensional parameter spaces in beyond-the-Standard Model theories. We evaluate the model likelihood for any choice of parameters by sampling the theory parameters intelligently…

High Energy Physics - Phenomenology · Physics 2023-03-08 Carlos A. Argüelles , Nicolò Foppiani , Matheus Hostert

Particle Markov Chain Monte Carlo methods are used to carry out inference in non-linear and non-Gaussian state space models, where the posterior density of the states is approximated using particles. Current approaches usually perform…

Computation · Statistics 2019-09-30 Eduardo F. Mendes , Christopher K. Carter , David Gunawan , Robert Kohn

We explore the sensitivity of several core-level spectroscopic methods to the underlying atomistic structure by using the water molecule as our test system. We first define a metric that measures the magnitude of spectral change as a…

Chemical Physics · Physics 2022-06-22 Johannes Niskanen , Anton Vladyka , Joonas Niemi , Christoph J. Sahle

The local dimension spectrum provides a framework for quantifying the fractal properties of a measure, and it is well understood for non-overlapping self-similar measures. In this article, we study the local dimension spectrum for dominated…

Dynamical Systems · Mathematics 2026-01-21 Alex Batsis , Antti Käenmäki , Tom Kempton

The spectral representation separates the contributions of geometrical arrangement (topology) and intrinsic constituent properties in a composite. The aim of paper is to present a numerical algorithm based on the Monte Carlo integration and…

Other Condensed Matter · Physics 2007-05-23 Enis Tuncer

Gaussian time-series models are often specified through their spectral density. Such models present several computational challenges, in particular because of the non-sparse nature of the covariance matrix. We derive a fast approximation of…

Computation · Statistics 2012-11-20 Nicolas Chopin , Judith Rousseau , Brunero Liseo

The object of this work is to design an adequate regularization for the problem of recovering missing Fourier coefficients, particularly in some non standard situations were low frequency coefficients are lost. In the framework of non-local…

Numerical Analysis · Mathematics 2014-02-04 Antonin Chambolle , Khalid Jalalzai

The Pseudo-Marginal (PM) algorithm is a popular Markov chain Monte Carlo (MCMC) method used to sample from a target distribution when its density is inaccessible, but can be estimated with a non-negative unbiased estimator. Its performance…

Computation · Statistics 2025-09-30 Sarra Abaoubida , Mylène Bédard , Florian Maire

Here we describe an advanced multi functional, variable-energy positron beam system capable of measuring the energies of multiple positron-induced electrons in coincidence with the Doppler-shifted gamma photon resulting from the…

A Python program has been developed which fits a published detector-response model to SiPM charge spectra to characterise SiPMs. Spectra for SiPMs illuminated by low intensity pulsed light with Poisson-distributed number of photons and a…

Instrumentation and Detectors · Physics 2023-01-30 Jack Rolph , Erika Garutti , Robert Klanner , Tobias Quadfasel , Joern Schwandt

We investigate, if the cosmic ray positron fraction, as reported by the HEAT and AMS collaborations, is compatible with the annihilation of neutralinos in the supergravity inspired Constrained Minimal Supersymmetric Model (CMSSM), thus…

Astrophysics · Physics 2009-11-07 W. de Boer , C. Sander , M. Horn , D. Kazakov

The cross over from low to high carrier densities in a many-polaron system is studied in the framework of the one-dimensional spinless Holstein model, using unbiased numerical methods. Combining a novel quantum Monte Carlo approach and…

Strongly Correlated Electrons · Physics 2007-05-23 M. Hohenadler , D. Neuber , W. von der Linden , G. Wellein , J. Loos , H. Fehske

This paper proposes new nonparametric diagnostic tools to assess the asymptotic validity of different treatment effects estimators that rely on the correct specification of the propensity score. We derive a particular restriction relating…

Methodology · Statistics 2019-02-11 Pedro H. C. Sant'Anna , Xiaojun Song